Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$153.31	10.270%	$169.0549	$169.05	$169.05	$169.10
Purchase #2	$147.38	7.465%	$158.3819	$158.38	$158.40	$158.40
Purchase #3	$231.58	13.214%	$262.181	$262.18	$262.20	$262.20
Purchase #4	$35.77	6.536%	$38.1079	$38.11	$38.10	$38.10
Purchase #5	$136.60	13.601%	$155.179	$155.18	$155.20	$155.20
Purchase #6	$98.32	11.328%	$109.4577	$109.46	$109.45	$109.50
Purchase #7	$45.47	6.284%	$48.3273	$48.33	$48.35	$48.30
7 purchase totals =	$848.43		$940.6897	$940.69	$940.75	$940.80